It is well known to coat a metallic surface with a polymer powder. For this purpose, various resin powder are widely used. Heretofore, as polyester powdered paints, amorphous polymer powder obtained by copolymerizing various acids or diols with polyethylene terephthalate has been used in order to coat the metallic surface. With regard to crystalline polyester polymers, resins per se are superior in various characteristics to the amorphous polymers. However, they have been considered to be quite unsuitable as powder paints from the viewpoint of adhesiveness to the metallic surface. Since conventional polyester powdered paints are amorphous polymers having a high second-order transition point, they are locking in extensibility. Thus, when coated metal goods such as metal pipes are subjected to after-processing such as bending, coating films are immediately cracked. There have not been known powdered paints including polyester powdered paints providing a coating film which could not be damaged even when subjected to a processing such as bending or pressing.
Study has long been made to obtain a high-performance powdered paint giving a coating film which is not damaged even when subjected to a processing such as bending.
We have now found that when high-molecular powder composed of a specified crystalline polyester is used, there can be obtained a high-performance coating film which has good adhesiveness to a metallic surface and can withstand after-processing such as bending.